A conventional high-frequency attenuation cable capable of preventing EMI (electromagnetic interference) has been proposed (see, e.g., PTL 1).
In this high-frequency attenuation cable, a magnetic tape formed of a magnetic material is helically wound around a conductor wire so as to partially overlap. In this configuration, electromagnetic noise emitted from the conductor wire is attenuated by the magnetic tape, and it is also possible to maintain flexibility. The magnetic tape is generally formed by a slitting process, i.e., by cutting a long and wide sheet to a constant width, which is then wound on a roller or reel.